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Autism: Making the Diagnosis

With no medical tests available, diagnosing autism requires careful observation and screening.
WebMD Feature
Reviewed by Louise Chang, MD

Diagnosing autism or autism spectrum disorders (ASD), a group of brain-based disorders that become apparent in early childhood, is often no simple task for a number of reasons.

No specific medical tests are available to diagnose ASD, so the diagnosis is made based on the observations of parents, physicians, and others, along with assessments of developmental progress.

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One in 150 children is now affected with ASD, according to the CDC. Because ASD is on a spectrum, many children are mildly affected, with less severe symptoms. So the behaviors that typically point to ''classic" autism may not be as pronounced or may be absent, says Paul Shattuck, PhD, an autism researcher at Washington University in St. Louis.

Further complicating things, autism is often accompanied by other problems, such as gastrointestinal ailments, hearing impairment, or behavior problems. "Autism often comes with something else," Shattuck says.

The age at which ASD is diagnosed can vary greatly, says Shattuck. In some children, he says, the disorder is apparent at 18 months. "You just know," he says. With other children, the autism diagnosis may not be confirmed until age 5 or so.

Parents can educate themselves about the typical symptoms, realizing that not every child has all the same symptoms or the same severity of symptoms. In general, children with ASD are socially impaired, may have language or communication difficulties, and exhibit some unusual behaviors, such as avoiding eye contact, resisting changes in routine, or declining to cuddle or have other human contact.

Parents who pay careful attention and who know what to look for can become aware of certain "red flags" that demand immediate professional attention, even if they don't turn out to be ASD symptoms, according to the American Academy of Pediatrics. Among them: the child arches his back instead of snuggling when picked up; doesn't make much eye contact, or loses language or social skills at any age.

Pay attention, too, to everyday interactions, Shattuck says. A toddler who never wants to be held, for instance, is a warning sign and something to talk to your pediatrician about as soon as possible. If language skills seem to be lagging, that's a concern. A 15-month-old, for instance, should be able to say single words; a 24-month-old should be able to say two-word phrases.

Your pediatrician should be on the lookout for any abnormal development clues when you take your child in for well-baby visits.

Diagnosing ASD requires two steps, according to the CDC:

  • Developmental screening and surveillance during well-child visits to the doctor. Screening tests to look for developmental disabilities and to be sure your child has met developmental "milestones" such as talking and walking are recommended at ages 9 months, 18 months, 24 months, and 30 months. The screenings should be done routinely; if not, parents are advised to ask for them during the well-child visits. The screening helps your child's pediatrician identify possible developmental delays that might suggest autism or such problems as language or thinking skill deficits. In recent years, screening tools have been developed to better identify children not just with classic autism but with milder forms of ASD, such as Asperger's syndrome. A variety of standardized screening tools is available. Typically, they employ a checklist or questionnaire format and have a cutoff "score."
  • A comprehensive evaluation, including observations by your pediatrician and interviews with you as parents to find out more about your child's developmental history. It should also include assessment of language and speech and the use of one or more autism diagnostic tools. Among them are the Autism Diagnosis Interview, the Childhood Autism Rating Scale, and The Gilliam Autism Rating Scale.

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